Posted by
G3VVT on
Jul 09, 2004; 10:52am
URL: http://elecraft.85.s1.nabble.com/Keying-a-Hercules-from-K2-tp368633p368635.html
It would be possible to do this switching with the K2 Amplifier Keying
Circuit in Elecraft application notes and adding a PNP transistor and a resistor
to provide the correct switching. This could be installed external to the K2
possibly at the TenTec Hercules amplifier keying input.
We used a similar circuit when constructing VHF/UHF repeaters from surplus
two way radios which use a +ve PTT keying circuit. The NPN output transistor
in the K2 keying circuit would be connected to the base of the extra PNP
transistor via a 4.7K resistor, the emitter of which is connected to the necessary
+ve line and the collector goes to your +ve keying line in the amplifier.
The method of operation is when the keying output from the K2 goes to ground
this biases on the PNP transistor that connects the keying circuit in the
TenTec amp to 12V +ve or whatever you use. This transistor provides the isolation
between the different voltages of the K2 (6V) and the TenTec (12V) in use in
the respective keying circuits.
If felt necessary you could add a pull up resistor of say 10K on the K2
keying output, though we never found this necessary and the prototype repeater
that used this circuit has been running on a hill top for many years.
Regards,
Bob, G3VVT
K2 #4168
_______________________________________________
Elecraft mailing list
Post to:
[hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft Help:
http://mailman.qth.net/subscribers.htmElecraft web page:
http://www.elecraft.com